feat(builtins): add http command (non-standard, HTTPie-inspired)

[chaliy]

Summary

A non-standard builtin for intuitive HTTP requests, inspired by HTTPie. curl is powerful but its flags are cryptic. http provides a human-friendly interface for the common case: API calls with JSON bodies.

Proposed Syntax

http [METHOD] URL [HEADER:value...] [field=value...] [field:=json...]

Key Differences from curl

Feature	curl	http
GET request	curl -s https://api.example.com	http GET api.example.com
POST JSON	curl -X POST -H 'Content-Type: application/json' -d '{"name":"x"}'	http POST api.example.com name=x
Auth header	curl -H 'Authorization: Bearer tok'	http api.example.com Authorization:Bearer\ tok
Pretty output	curl -s | jq .	Built-in (default)

Conventions

Syntax	Meaning
field=value	JSON string field
field:=123	Raw JSON value (number, bool, array, object)
field:=true	JSON boolean
Header:value	Request header (colon in key position)
==	Query parameter: page==2 → ?page=2

Use Cases

# GET with pretty output
http GET api.example.com/users

# POST with JSON body (automatic Content-Type)
http POST api.example.com/users name=Alice age:=30 active:=true

# With auth
http GET api.example.com/me Authorization:"Bearer $TOKEN"

# Query params
http GET api.example.com/search q==bashkit page==1

# Pipe JSON body
echo '{"bulk": true}' | http POST api.example.com/import

# Download
http GET example.com/file.tar.gz > file.tar.gz

llm_hint()

Some("http: HTTPie-style requests. `http GET url`, `http POST url key=val key:=123`. Auto JSON, pretty output. Use curl for advanced needs.")

Implementation Notes

• Reuses existing HTTP client infrastructure (allowlist still applies)
• Default method is GET if URL-only, POST if body fields present
• Auto-sets Content-Type: application/json when body fields used
• Pretty-prints JSON responses by default (with colors if possible)
• --raw flag to disable pretty printing
• NOT a replacement for curl — curl handles file uploads, custom protocols, certs

[chaliy]

Documentation Requirements

Since this is a non-standard (invented) builtin, it must be documented in two places:

1. README.md — Add to the "Built-in Commands" table under a new Extensions category row (non-standard bashkit-specific commands, clearly marked as extensions)
2. crates/bashkit/docs/extensions.md — Create or update a dedicated extensions guide covering all invented builtins, with short descriptions, examples, and rationale for why each exists

This ensures users discover these commands and understand they are bashkit-specific, not standard Bash.

[chaliy]

Resolved in PR #585 or #588